In the petroleum refining and petrochemical industry lot of olefinic naphtha streams are generated through various thermal and catalytic cracking processes such as delayed coking, steam cracking, fluid catalytic cracking (FCC), visbreaking etc. These processes generates olefinic naphtha streams comprising wide range of olefinic components from C5 to C14 and higher. Conventional TAME process involves various steps that include separation of the C5 fraction from FCC naphtha, de-sulfurize the C5 fraction, selective di-olefin saturation, TAME reaction and methanol separation cum recycling. Methanol is always used in excess to achieve the equilibrium conversion. Some of the prior art describes the method to route the excess methanol in the second reactor for conversion into lighter olefins or gasoline.
Etherification of isoamylenes mainly 2-methyl-1-butene and 2-methyl-2-butene is a well-known process which utilizes acidic catalytic system for production of Tertiary amyl methyl ether (TAME). This reaction is exothermic. In order to suppress the side reaction and also to improve the yield of TAME, methanol is always kept in excess over the stoichiometric ratio required for TAME production.
EP0498975A1 discloses a process for conversion on isoamylene into TAME by reacting with methanol in presence of modified acidic smectite clay catalysts.
EP0718269A1 describes a process for production of tertiary alkyl ethers by feeding C5 hydrocarbon stream to an etherification reactor and recycling the remaining stream in the same reactor after converting the linear pentenes into reactive isoamylenes.
U.S. Pat. No. 4,361,422 discloses a process for hydrogenation and etherification of unsaturated C5 streams to increase the octane number and to decrease the mono-olefin content.
U.S. Pat. No. 4,826,507 discloses a process for conversion of C4+ isoalkenes into ethers rich in MTBE and TAME by using excess methanol in the feed. The excess methanol was not recycled as per the conventional methods, however it is passed for concurrent conversion with the portion of effluent stream to conversion reactor wherein the presence of zeolite catalyst system, the alcohols and the olefins present in the stream are converted to gasoline. The second portion of the reactor section is generally called as methanol to gasoline process (MTG).
U.S. Pat. No. 5,166,455 discloses a process for conversion of C5-C7 olefinic hydrocarbons such as those contained in FCC light naphtha to isobutene and isoamylene rich streams for production for MTBE and TAME. The process involves the initial separation of C5 fraction of the feed stream which is converted to TAME. The C6-C7 fraction plus un-reacted C5's are converted into isobutylene and isoamylene rich stream by cracking with medium pore zeolite catalyst which is then used as feed stream for etherification to MTBE and TAME.